Very risky based on my own experiences. My situation was the same as yours but I was checked in the small room and almost could not come back. Be cautious if possible.
Before I left to Canada, I consulted with our immigration and visa officer in our university. She was very confident that I did not need the visa to come back. However, her understanding is totally different with what the border officers understood on the rules. Finally, the border officer very reluctantly let me in and took away my original I-94 form (white one).